Thermal characteristics of ferronickel slag on roasting process with addition of sodium carbonate (Na₂CO₃)

Abstract

Thermal characterization of ferronickel slag waste has been studied using TG / DTA, XRD, and SEM-EDX. The characterization of the initial samples of ferronickel slag was carried out TG / DTA to 1200°C. The result obtained is at a temperature of 800°C, there is an increasing mass and up to 4.68% at a temperature of 1200°C. At temperature of 807.4°C to 845.8°C, an exothermic reaction occurs. The increasing mass is due to the ferronickel slag which is originally in the form of metal, and then it was roasted to undergo an oxidation reaction so that the metal that has been formed, it returned into oxides. So that the weight of the sample mass increase. Samples of ferronickel slag added with sodium carbonate were also analyzed using TG / DTA. The results obtained are 2 endothermic peaks at temperatures of 90.6°C and 858.9°C with a total mass reduction of 49.3%. At a temperature of 90.6°C, there is a heavy loss caused by 2.38% loss of surface water. The XRD result of ferronickel slag is composed of enstatite (MgSiO3), forsterite (Mg2SiO4), fayalite (Fe2SiO4), and quartz (SiO2) structures. From the XRD analysis, the composition of silica oxide associates with magnesium and iron in the form of enstatite, forsterite, and fayalites is a very dominant composition. The roasting process of a mixture of ferronickel slag with sodium carbonate was carried out by heating at a temperature of 800-1000°C for 1 hour, and the sample result of roasting were analyzed using XRD. The result of roasting shows that the roasting process takes place more perfectly at higher temperature; it is indicated by the increasing phase intensity of SiO2 and the formation of sodium silicate (Na2SiO3). The result of SEM shows that the higher the temperature, the distribution of Na, Si, and O elements tend to cluster in the same place or spot, while the elements of Mg, Si, and O are less bonded.

Reverse leaching of magnesium from ferronickel slag using alkali solvent NaOH

“…Several studies with pyrometallurgical processes are by roasting or reducing ferronickel slag with a mixture of additives NaOH [13], Na 2 CO 3 [18] and Na 2 SO 4 [12]. The roasting process is carried out by adding an additive of Na 2 CO 3 for the decomposition of forsterite and enstatite into magnesium oxide and sodium silicate so that it will facilitate the process of separating precious metals, especially magnesium [4]. The hydrometallurgical process using the nickel slag leaching method was carried out at a leaching temperature of 140-200 °C with sulfuric acid as a leaching agent.…”

“…Secondly, the calcination process was carried out at a temperature of 800 °C for 60 minutes using a carbolite type of muffle furnace. The temperature and calcination time conditions are based on previous studies conducted from TG/DTA analysis towards ferronickel slag [4]. This calcination process is carried out to remove crystal water and to increase the porosity of the slag so it will facilitate the leaching process.…”

“…Some secondary sources that can be used from the byproduct of slags in the metallurgical process are tin slags, steel slags, aluminum slags, and ferronickel slags. The ferronickel slag is a byproduct of the smelting of nickel ores categorized as hazardous and poisonous to the environment [4]. The current use of ferronickel slag is only as construction material and most of its remaining slags are only piled around its environment [5][6][7][8][9].…”

“…The ferronickel slag still contains some valuable minerals such as silica, magnesium, nickel, iron, cobalt and some rare-earth elements [4,[10][11][12][13][14]. The major element content in the ferronickel slag is Si about 30 %, others are 20 % of Mg, 12 % of Fe, 1-2 % of Al, and other elements [15].…”

Magnesium extraction of ferronickel slag processed by alkali fusion and hydrochloric acid leaching

“…Prior research studies to increase the value of the ferronickel slag have been carried out using pyrometallurgy process [12][13][14] hydrometallurgy process [15,16] as well as combination of both processes [17][18][19]. Generally, flotation process is a commercially pre-tratment that carried out prior pyrometallurgy or hydrometallurgy process to separate or upgrade the specific element.…”